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As seen in the photo, hidden moisture from two different sources was seen in the middle image. But, some of the moisture was not visible in the image on the far right. The dark spots on the ceiling are the moisture and the some of the moisture on the far right was not visible in the last image. One reason the moisture could not be seen is because the image was taken with a cheaper, poor quality camera that are flooding the market now a days (far right). As moisture evaporates it emits less and less of signature for the infrared camera to detect. This makes it more more difficult for a less sensitive camera to “see” the hidden moisture. Also, as the temperature difference between the dry area vs the moist area become very close to the same energy level, things become hard to “see”. So even if you have a lot of moisture, but the dry area and moist area become close to the same temperature, things can start to disappear. Less sensitive infrared cameras start to go blind, but a better camera will still find these hard to “see” areas much better. Not all infrared cameras are created equal. Knowing how to read the specs on an infrared camera before you buy and how to change your environment can enhance your ability to find hidden moisture defects by 1000%. When your infrared camera goes blind, you will not even know it. This does not serve you well and the poor client, who is paying you for the infrared scan, is not getting the level of service they deserve. Moisture is important to find because it can be conducive to mold, decay, wood destroying insects and electrical issues. There are many other types of defects that cannot be seen, in some cases, for the same reasons stated in this article. (thanks to William Wisegrades for the images).
My post wasn’t clear, sorry about that. At first glance it looks like the two images aren’t quite apples to apples. The image on right includes the hot light fixture. Is that hot light fixture a good 2nd reason the camera went blind?
The light fixture does affect the second image, because of the characteristics of the cheap imager. The cheap imager, you will notice has a much broader field of view (probably 45° vs 25° for the professional class imager), making it more difficult to focus on just the area in question. The other issue caused by the light with this imager is the lack of a user adjustable span control. Even if the light were within the frame of the professional imager, the operator can control the span to achieve the needed contrast to highlight the moisture.
So yes, the light fixture is a factor in blinding the second imager, but only because of the limitations inherent in that imager. It would not have affected the professional imager’s ability to show substantially sharper contrast in the hands of a competent operator.
This is one of the reasons that the professional thermographers here always urge inspectors to move up to imagers with greater inherent sensitivity, better lenses and user adjustable focus and span controls.
